Method for the compensation of tolerances between a stator and a rotor of a phase shifter for an adjustable camshaft

ABSTRACT

A method may be used to adjust a gap between a stator and a rotor of a phase shifter for an adjustable camshaft. The stator may be connected to an outer shaft, and the rotor may be connected to an inner shaft of the adjustable camshaft. When the rotor rotates in the stator, a phase position of the inner shaft is adjusted relative to a phase position of the outer shaft. A gap may be formed between sliding surfaces on the stator and rotor. The method may involve coating at least one of the sliding surfaces with a removable coating, assembling the phase shifter including a joining of the rotor in the stator, starting up the phase shifter by rotating the rotor in the stator, and adjusting the gap between the stator and the rotor by way of abrasion of at least a partial thickness of the coating.

The invention relates to a method for the compensation of tolerances between a stator and a rotor of a phase shifter for an adjustable camshaft, wherein the stator is connected to an outer shaft, and the rotor is connected to an inner shaft, of the adjustable camshaft, and therefore, when the rotor rotates in the stator, the phase position of the inner shaft is adjusted relative to the phase position of the outer shaft, and wherein a gap is formed between at least one sliding surface on the stator and at least one sliding surface on the rotor. Furthermore, the invention relates to a phase shifter with a stator and with a rotor, in which tolerances have been compensated for with the method according to the invention.

PRIOR ART

For example, DE 11 2012 001 009 T5 discloses a method for the compensation of tolerances between a stator and a rotor of a phase shifter, in which a torsion drive mechanism is provided which permits the adjustment of the vertical position and axial alignment of the inner camshaft with respect to the outer camshaft while a torsionally rigid coupling is maintained between the camshaft adjuster and the inner or outer camshaft of the concentric camshaft. The torsion drive mechanism is formed either from a flexible shaft coupling, a transversely divided driven gear, a transversely divided toothed ring gear, a transverse pin toothed wheel or a pin and slot combination drive. Disadvantageously, the torsion drive mechanism is of complicated design and requires additional construction space.

WO 2011/133452 A2 proposes the use of a flexible coupling element between the phase shifter and the camshaft, said coupling element being depicted differently by different exemplary embodiments, for example the coupling forms a flexible disk or a flexible ring, as a result of which alignment errors can be compensated for. Disadvantageously, a further component is necessary with the flexible coupling, and, because of the flexible connection between the rotor or stator of the phase shifter and the inner shaft or the outer shaft, vibrations may build up in the overall assembly between the camshaft and the phase shifter.

The stator is generally of cup-like design and generally has a first cover element and a second cover element. The rotor which is rotatable relative to the stator is accommodated between the cover elements. If the rotor is fastened to the inner shaft, for example with a fastening means, such as a screw, and if the stator is connected to the outer shaft, alignment errors of the inner shaft relative to the outer shaft are also transmitted to the position of the rotor within the stator of the phase shifter. Adding up of a plurality of tolerances which are formed in particular by the connecting points between rotor and inner shaft and between stator and outer shaft, but also by shape and position tolerances of the further components of the phase shifter with respect to one another, may lead to malfunctions even as far as to blocking of the phase shifter such that the rotor is no longer freely rotatable in the stator. If too large a gap is selected between the sliding surfaces of the rotor and of the stator, an excessive leakage flow of the oil with which the phase shifter is operated is caused. Substantially oil-tight pressure spaces should be able to be formed in particular between blades formed on the rotor and stators formed on the stator so as not to have a negative influence on the efficiency of the phase shifter. If too large a gap is selected, the leakage flow of the oil between rotor and stator is excessive, and, if too small a gap is selected, the above-described problem of jamming or blocking of the rotor in the stator increasingly occurs.

DISCLOSURE OF THE INVENTION

The object of the invention is the development of a method for the compensation of tolerances between a stator and a rotor of a phase shifter in an arrangement on an adjustable camshaft, said phase shifter being simply designed and as far as possible not requiring any additional components. Furthermore, the object of the invention relates to the provision of a phase shifter with tolerances between the stator and the rotor being compensated for in a simple manner.

This object is achieved starting from a method according to the known features of claim 1 and starting from a phase shifter according to the preamble of claim 7 with the characterizing features in each case. Advantageous developments of the invention are specified in the dependent claims.

The invention includes the technical teaching that the method comprises at least the following steps: coating at least one of the sliding surfaces with a removable coating; assembling the phase shifter, comprising the joining of the rotor in the stator; starting up the phase shifter by means of rotating the rotor in the stator, and adjusting the gap between the stator and the rotor by means of abrasion of at least a partial thickness of the coating.

The method according to the invention permits simple compensation for tolerances between a stator and a rotor of a phase shifter, wherein play-free movement between the rotor and the stator becomes possible by means of the method according to the invention. In the event of shape and positional deviations between the stator and the rotor, the residual coating thickness remaining after the removal is adjusted within the first period of the starting up of the phase shifter in such a manner that the rotor is only just not blocked in the stator and can rotate freely. The method according to the invention does not require that shape and positional deviations of the rotor in the stator in an arrangement on the inner shaft and on the outer shaft are corrected, but rather the desired gap which is as small as possible is adjusted by itself in such a manner that, after the end of the adjustment of the gap, the phase shifter permits the same functional effect as a phase shifter with an ideally dimensionally exact rotor and stator.

If the camshaft with the phase shifter is put into operation, the coating is partially or completely removed, at least when a tolerance deviation is present, in particular by means of wear caused in a controlled manner. At least the partial thickness of the coating is namely removed until an ideal gap is formed and until the coating is no longer abraded by the opposite sliding surface or coating on the opposite surface.

It is of particular advantage if the coating is removed by an abrasion process by means of the sliding surface opposite the coating when the camshaft is put into operation. The opposite surface can also be the surface of a further coating. The mechanically caused removal of the coating takes place primarily by means of an abrasion process and therefore by means of wear. For this purpose, the coating has a lower, and in particular significantly lower, hardness than the components of the phase shifter, i.e., for example, the material hardness of the rotor or of the stator.

According to an advantageous refinement, the coating is formed from an antifriction lacquer or from another appliable substance. The coating, for example the antifriction lacquer, is applied here to the full surface area of the sliding surface of the component, wherein advantageously the coating can also be applied only to a limited extent to partial regions, in particular to a locally limited extent to the sliding surface which runs up against the opposite sliding surface, and the wear-based removal can arise. Consequently, the stator does not have to be coated completely on the inner side and the rotor does not have to be coated completely on the outer side, and the coating is limited to partial regions and serves for the subsequent sliding movement on the opposite surface. For example, it is possible to provide a plurality of partial regions which are formed in a punctiform manner or at least to a locally limited extent on segments of the, for example, circular sliding surface by means of the coating on the stator or the rotor.

The method according to the invention provides for the phase shifter to be started up by starting up of the camshaft in order to at least partially remove the coating and in order to form the axial play, and the camshaft is started up, for example, only in an arrangement on a cylinder head of an internal combustion engine, i.e. in the later operating environment. The coating can be removed, for example, by customary starting up of the camshaft or of a camshaft module in which the camshaft is accommodated. Alternatively, even before the actual starting up of the camshaft on an internal combustion engine, the phase shifter is put into operation in a running-in state, in particular whenever use is made of coating substances which are not intended to subsequently enter the oil circuit of the internal combustion engine, wherein it is also conceivable to select a coating material which may be present in the oil circuit without said coating material causing damage. In an advantageous manner, however, the coating is formed by a substance which does not cause any damage due to the solid solution in the oil during operation of an internal combustion engine. The removed coating components which are produced as very fine particles are then deposited, for example, via filter systems in the internal combustion engine.

The invention is furthermore directed to a phase shifter with a stator and with a rotor for an adjustable camshaft, wherein the stator is connectable to an outer shaft, and the rotor to an inner shaft, of the adjustable camshaft, and wherein at least one gap is formed between at least one sliding surface on the stator and at least one sliding surface on the rotor, and it is provided according to the invention that at least one of the sliding surfaces comprises a coating which, by starting up of the phase shifter, is at least partially abrasively removable, and therefore a gap size corresponding to the function arises.

Within the context of the present invention, a gap size corresponding to the function arises if, with the gap size formed after the abrasion, a permanent phase shifter is formed which has minimal wear and minimal need for oil.

The stator and the rotor are advantageously designed to be jointly rotatable about a longitudinal axis, wherein the longitudinal axis in particular forms the axis of rotation of the camshaft. At least one of the sliding surfaces on the stator and/or one of the sliding surfaces on the rotor is designed here in such a manner that—at least in an idealized view and with marginal angular errors being disregarded—the longitudinal axis forms a surface normal on the sliding surface. Ideally, the surface normal in each case forms a surface normal on the sliding surface, and, if the rotor sits, for example with an angular error, on the inner shaft then, viewed in idealized form within the context of the arrangement of the sliding surface, the longitudinal axis likewise forms a surface normal on said sliding surface.

The coating is particularly advantageously designed to be removable from the sliding surface by abrasion. The abrasion operation here is advantageously designed in such a manner that it takes place only limited to a first operating period of the phase shifter, and the desired gap size, in particular between the rotor and the stator, already arises after a first abrasion.

According to an advantageous refinement of the phase shifter, the stator comprises a first cover element by means of which the stator is connectable to the outer shaft of the adjustable camshaft, wherein the coating is applied to the first cover element. In particular, the coating is applied to the inner side of the cover element, said inner side facing the arrangement of the rotor. Furthermore, there is the possibility that the stator has a second cover element opposite the first cover element, and, when the phase shifter is fitted, the rotor is located in an arrangement between the first cover element and the second cover element. The stator is at least partially closed here toward an outer side by means of the second cover element, and the coating is applied to the second cover element, in particular on the inner side. Consequently, the stator comprises two cover elements, of which at least one cover element comprises a sliding surface which is provided with the coating and is directed toward the rotor. In the same manner, the rotor also comprises a side surface which faces one of the cover elements and on which the coating is applied. This results in particular in the advantageous possibility of compensating for position and angular errors of the arrangement of the stator and/or of the rotor on the outer shaft or on the inner shaft.

ADVANTAGEOUS EXEMPLARY EMBODIMENT OF THE INVENTION

Further measures improving the invention are illustrated in more detail below together with the description of an advantageous exemplary embodiment of the invention with reference to the figures, in which:

FIG. 1 shows a schematic view of a phase shifter in an arrangement on an adjustable camshaft with idealized position and dimensional accuracy,

FIG. 2 shows a phase shifter in an arrangement on an adjustable camshaft with an axial offset of the rotor on the inner shaft,

FIG. 3 shows a phase shifter configured according to the invention with a coating on the inner side of the stator in order to carry out the method, and

FIG. 4 shows a phase shifter in an arrangement on a camshaft according to FIG. 3, wherein a coating is applied to the rotor of the phase shifter.

FIGS. 1 and 2 each show a phase shifter 1 in an arrangement on an adjustable camshaft 12 according to the prior art. FIG. 1 shows the phase shifter 1 with an idealized construction, and FIG. 2 shows the phase shifter 1 with dimensional deviations of the components in the position with respect to one another, and therefore the method according to the invention for compensating the tolerances which occur is used in order to correct the dimensional deviations which are shown and therefore the associated position errors for the actual function, i.e. to render said position errors non-detrimental without correcting the actual geometrical position errors, for example between rotor and stator.

The phase shifter 1 and the adjustable camshaft 12 are illustrated in simplified schematized form, and the phase shifter 1 has a stator 10 and a rotor 11. The stator 10 is constructed by way of example with a first cover element 20 and a second cover element 21, and located between the cover element 20 and 21 is an intermediate element 22 which can also be formed integrally with the first cover element 20 or with the second cover element 21.

The adjustable camshaft 12 has an outer shaft 13 and an inner shaft 14, and the outer shaft 13 and the inner shaft 14 and also the stator 10 and the rotor 11 are rotatable about a common longitudinal axis 18. The arrangement of the stator 10 on the outer shaft 13 is illustrated in simplified form above the first cover element 20. The connection between the rotor 11 and the inner shaft 14 comprises a fastening means 19, and the fastening means 19 is designed, for example, as a screwing element.

A comparable view of FIGS. 1 and 2 of the prior art indicates that a simple dimensional deviation of the end surface 23 of the inner shaft 14 already results in a considerable positional deviation of the rotor 11 in the stator 10. If the phase shifter 1 is put into operation, the latter either only carries out the function to a limited extent or even completely blocks said function. The limited function lies in the deviation of the gap 5 which is illustrated in idealized form in FIG. 1 and is therefore identical overall, and at the point shown in FIG. 2 may lead to blocking, for example due to the positional deviation of the rotor 11 in the stator 10.

The stator 10 comprises inner-side sliding surfaces 15, and the rotor 11 comprises outer-side sliding surfaces 16. During the operation of the phase shifter 1, the sliding surfaces 15 and 16 move on each other, and the gap 5 is required between the sliding surfaces 15 and 16 in order, by lubrication with oil, to permit the sliding surfaces 15 and 16 to slide on each other. If the gap 5 is not present and the rotor 11 jams, for example, only at one point or at opposite points in the stator 10, the phase shifter 1 blocks.

FIG. 3 shows a first exemplary embodiment of the phase shifter 1 according to the invention with a coating 17 on the inner-side sliding surfaces 15 on the stator 10. The rotor 11 is located here in an arrangement on the inner shaft 14, fastened with the fastening means 19, wherein the rotor 11 has positional errors. By means of the coating 17 used on the inner-side sliding surface 15 of the stator 10, when the phase shifter 1 is started up the rotor 11 works into the coating 17 by the coating 17 being abrasively removed over at least a partial thickness by the movement of the rotor 11. This results in a gap 5 which comprises a minimum air gap, and therefore, despite the positional deviation of the rotor 11 into the stator 10, disturbance-free operation of the phase shifter 1 takes place. The necessary removal of the partial thickness or of the entire thickness of the coating 17 takes place automatically here since, upon starting up, the coating 17 is removed by precisely the partial thickness until the required gap 5 arises.

The stator 10 has a first cover element 20 and a second cover element 21, and the coating 17 is applied, for example, to the inner sliding surface 15 of the two cover elements 20 and 21, i.e. the stator 10 is mounted with an oversize which reduces the receiving space for the rotor 11.

In a modification of FIG. 3, FIG. 4 shows an exemplary embodiment of the invention, in which the coating 17 is applied to the sliding surfaces 16 of the rotor 11, i.e. the rotor 11 is fitted with an oversize. The sliding surfaces 16 face the opposite inner surfaces of the stator 10, which inner surfaces are coated according to FIG. 3. Of course, there is also the possibility, in a combination of the exemplary embodiments of FIGS. 3 and 4, of providing a coating both of the sliding surfaces 15 on the stator 10 and of the sliding surfaces 16 on the rotor 11.

The removed material of the coating 17 is transported away in the oil of the phase shifter 1. The transporting away of the abrasively removed coating 17 enables a subsequently functionally reliable operation of the phase shifter 1.

The coatings 17 shown on the sliding surface 15 on the stator 10 according to FIG. 3 and on the sliding surface 16 of the rotor 11 according to FIG. 4 are merely possible exemplary embodiments for the application of a coating 17. Within the scope of the invention, a possibility is also provided of, for example, providing the intermediate element 22 of the stator 10 with a coating on the inner side, or the rotor 11 comprises an outer-side coating. Such a removable coating compensating in particular for a radial movement is required, for example, in the case of an axially offset arrangement of the stator 10 on the outer shaft 13 or of the rotor 11 on the inner shaft 14.

The invention is not restricted in its design to the advantageous exemplary embodiments indicated above. On the contrary, a number of different variants are conceivable which make use of the presented solution even in embodiments of fundamentally different type. All of the features and/or advantages revealed in the claims, the description or the drawings, including structural details or spatial arrangements, may be essential to the invention both by themselves and in very different combinations.

LIST OF REFERENCE SIGNS

-   1 Phase shifter -   5 Gap -   10 Stator -   11 Rotor -   12 Adjustable camshaft -   13 Outer shaft -   14 Inner shaft -   15 Sliding surface (on the stator) -   16 Sliding surface (on the rotor) -   17 Coating -   18 Longitudinal axis -   19 Fastening means -   20 First cover element -   21 Second cover element -   22 Intermediate element -   23 End surface 

1.-10. (canceled)
 11. A method for compensation of tolerances between a stator and a rotor of a phase shifter for an adjustable camshaft, wherein the stator is connected to an outer shaft and the rotor is connected to an inner shaft of the adjustable camshaft, wherein a phase position of the inner shaft is adjusted relative to a phase position of the outer shaft when the rotor rotates in the stator, wherein a gap is formed between a sliding surface on the stator and a sliding surface on the rotor, the method comprising: coating at least one of the sliding surface on the stator or the sliding surface on the rotor with a removable coating; assembling the phase shifter, which comprises a joining of the rotor in the stator; starting up the phase shifter by rotating the rotor in the stator; and adjusting the gap between the stator and the rotor by way of abrasion of at least a partial thickness of the removable coating.
 12. The method of claim 11 further comprising removing the removable coating by an abrasion process by way of the sliding surface on the stator or on the rotor opposite the removable coating when the adjustable camshaft is put into operation.
 13. The method of claim 11 wherein the removable coating comprises an applicable lacquer.
 14. The method of claim 11 wherein the removable coating comprises an antifriction lacquer.
 15. The method of claim 11 wherein the removable coating is applied to a partial region of at least one of the stator or the rotor.
 16. The method of claim 11 wherein the removable coating is applied to a limited extent to at least one of the sliding surface on the stator or the sliding surface on the rotor.
 17. The method of claim 11 wherein the starting up of the phase shifter occurs with a starting up of the adjustable camshaft in an arrangement on a cylinder head of an internal combustion engine.
 18. A phase shifter comprising a stator and a rotor for an adjustable camshaft, wherein the stator is connectable to an outer shaft of the adjustable camshaft and the rotor is connectable to an inner shaft of the adjustable camshaft, wherein a gap is formed between a sliding surface on the stator and a sliding surface on the rotor, wherein at least one of the sliding surface on the stator or the sliding surface on the rotor includes a coating, which by starting up of the phase shifter is removable by abrasion to an extent such that a size of the gap corresponds to a function.
 19. The phase shifter of claim 18 wherein the stator and the rotor are rotatable about a common longitudinal axis, wherein the sliding surface on the stator and the sliding surface on the rotor are configured such that the common longitudinal axis is a surface normal to the sliding surface on the stator and to the sliding surface on the rotor.
 20. The phase shifter of claim 18 wherein the coating is removable from the at least one of the sliding surface on the stator or the sliding surface on the rotor by way of abrasion.
 21. The phase shifter of claim 18 wherein the stator comprises a first cover element by way of which the stator is connectable to the outer shaft of the adjustable camshaft, wherein the coating is applied to the first cover element.
 22. The phase shifter of claim 21 wherein the stator comprises a second cover element disposed opposite the first cover element and by way of which the stator is at least partially closed toward an outer side, wherein the coating is applied to the second cover element.
 23. The phase shifter of claim 18 wherein the stator comprises a second cover element by way of which the stator is at least partially closed toward an outer side, wherein the coating is applied to the second cover element. 